The present invention relates to non-chrome passivating compositions employed as post-rinses in the preparation of phosphated metal substrates. Post-rinses or sealers enhance the corrosion resistance of metal substrates, particularly those that have been pretreated with phosphate conversion coatings. In the past many post-rinse compositions contained chromic acid. To further develop the post rinse technology considering environmental and safety areas from a formulation viewpoint rather than a processing viewpoint, it is desirable to replace those post-rinses with chromic acid with non-chrome post-rinses.
Post rinse technology has utilized certain solubilized metal ions other than chromium to enhance the corrosion resistance of phosphated metal substrates as shown in U.S. Pat. Nos. 3,966,502 and 4,132,572. U.S. Pat. No. 3,966,502. These metal ions can include: water-soluble zirconium salt, and fluorophosphate salt or a mixture of fluorophosphate salts. Also the technology has utilized in rinse compositions such organic, polymeric or nitrogen-containing materials as vegetable tannin, poly-4-vinylphenol or a derivative thereof, and a derivative of a polyalkenylphenol, all of which are used along with other specific components. Such rinse compositions as shown in U.S. Pat. Nos. 3,975,214; 4,376,000; and 4,517,028, respectively, provide enhancement of the corrosion resistance of phosphated metal substrates.
Several examples of rinse compositions with various specific combinations of components are available in the art. For example, the rinse composition of U.S. Pat. No. 3,615,895 has an aqueous alkali metal silicate solution prepared from the metal oxide of sodium or potassium; and a water soluble quaternary nitrogen compound having at least one nonhydroxylated alkyl group. Another example of an aqueous rinse composition is disclosed in U.S. Pat. No. 3,912,548 which has ammonium zirconium carbonate and ammonium fluorozirconate; and polyacrylic acid, esters, and salts thereof. U.S. Pat. No. 4,110,129 discloses an aqueous rinse composition with titanium ion and an adjuvant material selected from the group consisting of phosphoric acid, phytic acid, tannin, the salts or esters of the foregoing, and hydrogen peroxide. U.S. Pat. No. 4,457,790 discloses a rinse composition comprising a metal ion selected from the group consisting of titanium, hafnium and zirconium and a mixture thereof; and a polymeric material which is a derivative of a polyalkenylphenol. Also U.S. Pat. No. 5,209,788 discloses a method of treating metal substrates with an aqueous rinse composition comprising a Group IV-B metal compound from the Periodic Table of Elements; and an amino acid or an amino alcohol.
Many of the non-chrome rinses previously used or described in the post rinse technology do not match the performance of chromic acid rinses. The present invention provides a novel non-chrome post-rinse composition that can more closely match the performance of chromic acid rinses over commercially popular substrates.